Partial hydrogenation of conjugated diolefinic hydrocarbons



United States Patent 3,478,123 PARTIAL HYDROGENATION OF CONJ'UGATED DIOLEFINIC HYDROCARBONS John F. Brennan, Des Plaines, Ill., assignor to Universal Oil Products Company, Des Plaines, 11]., a corporation of Delaware No Drawing. Filed Oct. 13, 1967, Ser. No. 675,052

The portion of the term of the patent subsequent to May 20, 1986, has been disclaimed Int. Cl. C07c 11/16, 5/16 US. Cl. 260-677 6 Claims ABSTRACT OF THE DISCLOSURE Diolefinic hydrocarbons are partially hydrogenated by treatment with hydrogen in the presence of a ruthenium chloride catalyst whereby a mono-olefinic hydrocarbon is produced, said partial hydrogenation being accomplished without a concurrent isomerization whereby the double-bond is shifted to a more central location.

This invention relates to a process for the partial hydrogenation of conjugated diolefinic hydrocarbons, and particularly to a process for the partial hydrogenation of said hydrocarbons without a shift of the double-bond to a more central location in the chain. It has now been discovered that a partial hydrogenation of conjugated diolefinic hydrocarbons may be effected in which the hydrogen will add to the 1 and 2 carbon atoms rather than the 1 and 4 carbon atoms in a conjugated diolefinic chain. For purposes of this invention the term 1 and 2 carbon atoms will refer to adjacent carbon atoms containing the double-bond in a conjugated diolefinic system, and 1 and 4 carbon atoms will refer to the carbon atoms at each end of the conjugated diolefinic system. This may be illustrated utilizing 1,3-butadiene in which the carbon atoms are numbered as follows:

Thus, when effecting a partial hydrogenation according to the process of this invention, and by utilizing certain catalytic compositions of matter of a type hereinafter set forth in greater detail, a mono-olefinic hydrocarbon will be obtained in which only 1 of the double-bonds in a conjugated diolefinic system will be hydrogenated without a shift of the double-bond. Thus when 1,3-butadiene is partially hydrogenated according to the present process, hydrogen will add to the l and 2 carbon atoms of the chain and the resultant mono-olefinic hydrocarbon will be an ot-olefin. This is in contradistinction to other processes in which the hydrogen will add to the 1 and 4 carbon atoms and thus shift the double-bond to the 2 position in the chain. This is of importance where the desired product comprises an a-olefin rather than an olefin in which the double-bond is in an interior position in the chain. For example, when the desired product comprises l-butene it is possible to obtain this product from a mixture of refinery off-gases containing a mixture of 1,3-butadiene and isomeric butenes without having to go through a series of fractionation, hydrogenation and refractionation steps in order to obtain the desired product. The product l-butene is of commercial importance as an intermediate in the preparation of polymer and alkylate gasolines which will possess high octane numbers. Likewise, l-pentene is also used as a blending agent for the preparation of high octane motor fuel.

It is therefore an object of this invention to provide a process for the partial hydrogenation of conjugated diolefinic hydrocarbons Without a concurrent isomerization reaction taking place.

A further object of this invention is to provide a process for the partial hydrogenation of conjugated diolefinic hydrocarbons utilizing certain catalyst compositions of matter whereby isomerization of the remaining double-bond is avoided.

In one aspect an embodiment of this invention resides in a process for the partial hydrogenation of a conjugated diolefinic hydrocarbon without isomerization which comprises treating said hydrocarbon with hydrogen in the presence of a catalyst comprising ruthenium chloride at hydrogenation conditions, and recovering the resultant mono-olefinic hydrocarbon.

A specific embodiment of this invention is found in a process for the partial hydrogenation of 2-methyl-l,3- butadiene which comprises treating said 2methyl-1,3 butadiene with hydrogen in the presence of a catalyst comprising ruthenium chloride in which. said ruthenium component is present in a valence state of +2 and a temperature in the range of from about ambient to about 300 C. and a hydrogen pressure of from about 1 to about atmospheres, and recovering the resultant 2- methylbutene-l and 3-methylbutene-1.

Other objects and embodiments will be found in the following further detailed description of the present invention.

As hereinbefore set forth the present invention is concerned with a process for the partial hydrogenation of conjugated diolefinic hydrocarbons whereby only one double-bond of the hydrocarbon will he hydrogenated, thereby leaving a mono-olefinic hydrocarbon which contains the remaining double-bond in the original position on the carbon atom chain, rather than having a shift of the double-bond to a more central location on the chain occur during the hydrogenation process. The partial hydrogenation of the conjugated diolefin is effected by treating the diolefin with hydrogen in the presence of certain catalytic compositions of matter. In the preferred embodiment of the invention the catalyst comprises a ruthenium chloride in which the ruthenium component of the catalyst possesses a valence state of +2. The desired catalyst may be prepared by reducing a ruthenium compound in which the ruthenium component of the compound has valence of +3. A specific example of this is the reduction of ruthenium trichloride hydrate using hydrogen and a platinum metal catalyst in a Parr apparatus at a temperature of about 50 C. using an excess of sodium chloride in order to avoid complete reduction of the compound to ruthenium metal. llnasmuch as the ruthenium chloride complex in which the ruthenium is present in a valence state of +2 is easily oxidized to a compound in which the ruthenium is present in a valence state of +3, it is necessary to effect the process in an oxygen-free atmosphere. Therefore, it is necessary to remove any dissolved air by treatment with a nitrogen purge andin some instances, it may also be necessary to remove organic peroxides using a ferrous sulfate wash.

Examples of diolefinic hydrocarbons, and preferably conjugated diolefinic hydrocarbons which may be sub jected to partial hydrogenation according to the process of this invention are those which preferably contain from 4 to about 7 carbon atoms in the molecule and will include both straight chain and branch chain diolefins. Specific examples of these compounds will include 1,3-butadiene, 2-methyl-l,3-butadiene(isoprene), 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-l,3hexadiene, etc. The hydrogenation conditions will include a temperature in the range of from about ambient (25 C.) up to about 300 C. or more and a hydrogen. pressure in the range of from 1 to about 100 atmospheres.

The process of this invention may be effected in any suitable manner and may comprise either a batch or continuous type operation. For example, when a batch type operation is used, a quantity of the diolefinic hydrocarbon which is to undergo partial hydrogenation is placed in an appropriate reaction apparatus. Examples of the type of reaction vessels which may be used include hydrogenation bombs or autoclaves, either the rotating or mixing type. In addition, the ruthenium chloride catalyst in which the ruthenium component is present in a valence state of +2 is also added to the reaction vessel. As hereinbefore set forth care must be taken in order that the hydrocarbon feed stock is free of any dissolved air, organic peroxides or any other compounds containing oxygen. Therefore, the feed stock, before being placed in the reaction apparatus is dried by conventional means and subjected to a nitrogen purge in order that any contaminating infiuences which may be present in the feed stock are removed. In addition, the catalyst is also treated in a similar manner by undergoing a nitrogen purge. The reaction vessel is sealed, hydrogen is pressed in until the desired operating pressure hereinbefore set forth is reached and the vessel and contents thereof are thereafter heated until the desired operating temperature is reached. The hydrogenation is allowed to proceed for a predetermined period of time which may range from 1 up to about hours or more in duration. At the end of this time the reactor, if superatmospheric pressure has been used is cooled to a temperature of about 75 C. in order to avoid or minimize vaporization and hydrogen stripping losses when the vessel is opened and the excess pressure is vented. The reaction mixture is recovered, separated from the catalyst and thereafter subjected to convention separation means such as, for example, fractional distillation under reduced pressure whereby the desired mono-olefinic hydrocarbon containing 1 of the double-bonds in its original position in the chain is separated from any unreacted starting material. It is also contemplated Within the scope of this invention that, if so desired, the reaction may be eifected in the presence of substantially inert solvents which are used to facilitate the mixing of the reactants. Specific examples of these inert organic solvents which may be used include methyl alcohol, ethyl alcohol, propyl alcohol, n-pentane, n-hexane, n-heptane, benzene, toluene, o-xylene, m-xylene, p-xylene, etc.

It is also contemplated within the scope of this invention that the process may be effected in a continuous manner of operation. For example, when this type of operation is used, the feed stock comprising a conjugated diolefinic hydrocarbon is continuously charged to a reaction zone which is maintained at the proper operating conditions of temperature and pressure, the temperature and pressure being within the range hereinbefore set forth. Prior to entry into said reactor, the feed stock is treated in a manner similar to that hereinbefore set forth, that is, by being dried and purged with nitrogen in order to remove any contaminates which may have a deleterious eifect on the catalyst. The catalyst, comprising a ruthenium chloride complex in which the ruthenium has been reduced to and is in a valance state of +2 is also added to the reaction zone after undergoing a nitro gen purge. The aforementioned desired pressure is provided for by the introduction of hydrogen to the reaction vessel in an amount sufficient to maintain the pressure at which the process is effected. However, it is also contemplated that the hydrogen which is introduced into the reaction zone for the partial hydrogenation reaction may account for only a portion of the operating pressure, the remainder of said pressure being provided for by the use of an inert gas such as nitrogen to augment the hydrogen charge and thus provide the desired operating pressure. After completion of the desired residence time the reactor efliuent is continuously withdrawn from the reaction zone and subjected to a separation process by any manner done in the art whereby the desired product comprising a monoolefinic hydrocarbon containing one of the double-bonds in its original positions in the carbon atom chain is separated from unreacted starting material EXAMPLE 1 A catalyst comprising ruthenium chloride in which the ruthenium component was present in a valence state of +2 was prepared by reducing ruthenium trichloride hydrate by treating said complex with hydrogen in the presence of a platinum catalyst in a Parr apparatus at 50 C. In addition, an excess of 3 molar sodium chloride was present in order to avoid complete reduction of the complex to ruthenium metal.

A hydrocarbon charge stock comprising 2- methyl-1,3-'

butadiene (isoprene) was treated prior to introduction into the reaction vessel comprising a hydrogenation bomb by purging said hydrocarbon with nitrogen in order to remove any dissolved air which may have been present in the charge stock. The vessel was sealed and hydrogen pressed in until an initial pressure of 5 atmospheres was reached. The reaction was allowed to proceed at ambient temperature and the aforementioned pressure for a period of 24 hours, At the end of this time the hydrogenation bomb was cooled to a temperature of about 75 C. in order to minimize vaporization and hydrogen stripping losses when the bomb was depressurized. The excess pressure was vented and the reaction product was recovered. The product was subjected to analysis, said analysis disclosing the product of a major portion of Z-methylbutene- 1 with some 3-methylbutene-1 being present.

EXAMPLE II In this example a catalyst is prepared in a manner similar to that set forth in Example I above. A feed stock comprising 1,3-butadiene is purged with nitrogen to remove any dissolved air which may be present in the feed stock and charged to a hydrogenation bomb containing the catalyst in which the ruthenium component is in a valence state of +2. Hydrogen is pressed into the bomb until an initial pressure of 25 atmospheres is reached. The bomb is then heated to a temperature of about 50 C. and maintained thereat for a period of 10 hours. At the end of this time the bomb is cooled to a temperature of -75 C. in order to minimize vaporization and stripping losses. Thereafter the bomb is depressurized and opened, the reaction product is recovered and subjected to analysis which will disclose a major portion of the product comprising butene-l.

EXAMPLE III A catalyst is prepared by reducing ruthenium trichloride hydrate by treatment with hydrogen in the presence of a platinum metal catalyst, said solution being stabilized by using a molecule excess of sodium chloride. The catalyst is purged with nitrogen and placed in a hydrogenation bomb along with a charge stock comprising 1,3-pentadiene, said feed stock having also been purged with nitrogen to remove any oxidation contaminates which may be present. The bomb is sealed and hydrogen pressed in until an initial pressure of 25 atmospheres is reached. The bomb is then heated to a temperature of about C. and maintained thereat for a period of 10 hours. At

the end of this time the bomb is treated in a manner similar to that set forth in the above examples, that is, by being cooled at a temperature of about 75 C. in

order to minimize vaporization and hydrogen stripping jugated diolefinic hydrocarbon without isomerization which comprises treating said hydrocarbon with hydrogen in the presence of a catalyst comprising ruthenium chloride at hydrogenation conditions, and recovering the resultant mono-olefinic hydrocarbon.

2. The process as set forth in claim 1, further characterized in that said ruthenium component of said catalyst is in a valence state of +2.

3. The process as set forth in claim 1, further characterized in that said hydrogenation conditions include a temperature in the range of from about ambient to about 300 C. and a hydrogen pressure of from about 1 to about 100 atmospheres.

4. The process as set forth in claim 1, further characterized in that said conjugated diolefinic hydrocarbon comprises 2-methyl-l,3-butadiene and said mono-olefinic hydrocarbon comprises primarily 2-methylbutene-1.

5. The process as set forth in claim 1 further characterized in that said conjugated diolefinic hydrocarbon comprises 1,3-butadiene and said mono-olefinic hydrocarbon comprises a major portion of butene-l.

6. The process as set forth in claim 1, further characterized in that said conjugated diolefinic hydrocarbon comprises 1,3-pentadiene and said mono-olefinic hydrocarbon comprises a major portion of pentene-l.

References Cited UNITED STATES PATENTS 3,408,415 10/1968 Dovell et al 260-666 2,944,094 7/1960 Rylander et a1. 260677 3,268,608 8/1966 Rosset 260668 DELBERT E. GANTZ, Primary Examiner I. D. MYERS, Assistant Examiner US. Cl. X.R. 260683.9 

